Why is there still blue smoke after replacing the engine?

[RoseLee]

Blue smoke indicates oil burning, and the main reasons for oil burning are as follows: Unqualified engine oil: Low-quality engine oil can accelerate wear. Additionally, if the oil viscosity is too low or too high, it can lead to poor engine lubrication, increasing wear on the piston rings and cylinder walls, reducing sealing performance, and resulting in oil burning. Excessive clearance: Excessive clearance between the piston rings and cylinder walls, improper installation of piston rings, or degraded sealing performance can allow oil on the cylinder walls to enter the combustion chamber, causing oil burning. Furthermore, poor sealing performance of the valve seals, damage to the Positive Crankcase Ventilation (PCV) valve, or clogged crankcase ventilation ports can increase pressure in the crankcase, causing oil to enter the cylinders along with crankcase gases and participate in combustion.